Thirteen escape in prison break near Manila

The Philippines has frequently suffered mass escapes from prisons which are usually overcrowded [File: Reuters]

At least 13 "high-value" detainees facing drug charges have escaped from a jail in northern Philippines, the latest in a series of prison breaks in the country, according to authorities.

The escapees slipped out of the jail in a police camp in San Fernando City, north of the capital, Manila, before dawn on Sunday.

"They sawed through the bars of the metal grille," Derrick Arnold Carreon, spokesman for the Philippine Drug Enforcement Agency, told the AFP news agency, adding that an investigation was under way to find out how they got the saw.